Bifurcated stent and method for the manufacture of same

ABSTRACT

An expandable bifurcated stent comprising a proximal end and a distal end in communication with one another. The proximal end comprises a primary passageway and the distal end comprises a pair of secondary passageways. The stent is expandable from a first, contracted position to a second, expanded position upon the application of a radially outward force exerted on the stent. Each of the primary passageway and the secondary passageway being constructed of a tubular wall having a porous surface, a method for production of a bifurcated stent is also described. The method comprises the step of connecting a first stent section to a second stent section, the first stent section having an end thereof adapted for connection to an opening disposed along the length of a second stent section.

TECHNICAL FIELD

The present invention relates to a bifurcated stent and to a method forthe manufacture and delivery of a bifurcated stent.

BACKGROUND ART

Stents are generally known. Indeed, the term “stent” has been usedinterchangeably with terms such as “intraluminal vascular graft” and“expansible prosthesis”. As used throughout this specification the term“stent” is intended to have a broad meaning and encompasses anyexpandable prosthetic device for implantation in a body passageway(e.g., a lumen or artery).

In the past six to eight years, the use of stents has attracted anincreasing amount of attention due the potential of these devices to beused, in certain cases, as an alternative to surgery. Generally, a stentis used to obtain and maintain the patency of the body passageway whilemaintaining the integrity of the passageway. As used in thisspecification, the term “body passageway” is intended to have a broadmeaning and encompasses any duct (e.g., natural or iatrogenic) withinthe human body and can include a member selected from the groupcomprising: blood vessels, respiratory ducts, gastrointestinal ducts andthe like.

Initial stents were self-expanding, spring-like devices which wereinserted in the body passageway in a contracted state. When released,the stent would automatically expand and increase to a final diameterdependent on the size of the stent and the elasticity of the bodypassageway. Such stents are known in the art as the Wallstent™.

The self-expanding stents were found by some investigators to bedeficient since, when deployed, they could place undue, permanent stresson the walls of the body passageway. This lead to the development ofvarious stents which were controllably expandable at the target bodypassageway so that only sufficient force to maintain the patency of thebody passageway was applied in expanding the stent.

Generally, in these later systems, a stent, in association with aballoon, is delivered to the target area of the body passageway by acatheter system. Once the stent has been properly located (the targetarea of the body passageway can be filled with a contrast medium tofacilitate visualization during fluoroscopy), the balloon is expandedthereby expanding the stent, e.g. by plastic deformation of the stentstructure, so that the latter is urged in place against the bodypassageway. As indicated above, the amount of force applied is at leastthat necessary to maintain the patency of the body passageway. At thispoint, the balloon is deflated and withdrawn within the catheter, andsubsequently removed. Ideally, the stent will remain in place andmaintain the target area of the body passageway substantially free ofblockage (or narrowing).

A stent which has gained some notoriety in the art is known as thePalmaz-Schatz™ Balloon Expandable Stent (hereinafter referred to as “thePalmaz-Schatz stent”). This stent is discussed in a number of patentsincluding U.S. Pat. Nos. 4,733,665, 4,739,762, 5,102,417 and 5,316,023,the contents of each of which are hereby incorporated by reference.

Another stent which has gained some notoriety in the art is known asGianturco-Roubin Flex-Stent™ (hereinafter referred to as “theGianturco-Roubin stent”). This stent is discussed in a number of patentsincluding U.S. Pat. Nos. 4,800,882, 4,907,336 and 5,041,126, thecontents of each of which are hereby incorporated by reference.

Other types of stents are disclosed in the following patents:

U.S. Pat. No. 5,035,706 (Gianturco et al.),

U.S. Pat. No. 5,037,392 (Hillstead),

U.S. Pat. No. 5,147,385 (Beck et al.),

U.S. Pat. No. 5,282,824 (Gianturco),

Canadian patent 1,239,755 (Wallsten), and

Canadian patent 1,245,527 (Gianturco et al.), the contents of each ofwhich are hereby incorporated by reference.

All of the stents described in the above-identified patents share thecommon design of being mono-tubular and thus, are best suited to bedelivered and implanted in-line in the body passageway. These knownstents are inappropriate for use in a bifurcated body passageway (e.g. abody passageway comprising a parent passageway that splits into a pairof passageways). Further, these stents are inappropriate for use in abody passageway having side branches since: (i) accurate placement ofthe stent substantially increases the risk to the patient, (ii) the riskof passageway closure in the side branches is increased, and (iii) theside branches will be substantially inaccessible.

Indeed the Physician Guide published in support of the Palmaz-Schatzstent states on page 32 (the contents of which are hereby incorporatedby reference):

“ . . . no attempt should be made following placement of a PALMAZ-SCHATZstent to access the side branch with a guide wire or a balloon, as suchattempts may result in additional damage to the target vessel or thestent. Attempts to treat obstructed side branches within stentedsegments can result in balloon entrapment, necessitating emergencybypass surgery.”

Thus, when installed, the Palmaz-Schatz stent admittedly shields sidebranches emanating from the target area of the body passagewayeffectively permanently. This can be problematic since the only way totreat blockage or other problems associated with the side branches is toperform the type of surgery which installation of the stent was intendedto avoid.

This contraindication for conventional mono-tubular stents iscorroborated by a number of investigators. See, for example, thefollowing:

1. Interventional Cardiovascular Medicine: Principles and Practice(1994); Publisher: Churchill Livingstone Inc.; pages 221-223 (Ohman etal.), 487-488 (Labinaz et al.), 667-668 (Bashore et al.) and 897 (Baileyet al.), including references cited therein;

2. Gianturco-Roubin Flex-Stent™ Coronary Stent: Physician's Guide; page2, Paragraph 3 under WARNINGS;

3. Circulation, Vol. 83, No. 1, January 1991 (Schatz et al.); entitled“Clinical Experience With the Palmaz-Schatz Coronary Stent”; pages148-161 at page 149; and

4. American Heart Journal, Vol. 127, No. 2, February 1994 (Eeckhout etal.); entitled “Complications and follow-up after intracoronarystenting: Critical analysis of a 6-year single-center experience”; pages262-272 at page 263,

the contents of each of which are hereby incorporated by reference.

Further, some investigators have attempted to install individual stentsin each branch of the bifurcated body passageway. However, this approachis fraught with at least two significant problems. First, implantationof three individual stents, together with the expansive forces generatedupon implantation results in subjecting the central walls of thebifurcated body passageway to undue stress which may lead topost-procedural complications. Second, since the central walls of thebifurcated body passageway are not supported by the individual stents,this area of the passageway is left substantially unprotected andsusceptible to blockage.

One particular problem area with bifurcated body passageways is theoccurrence of bifurcation lesions within the coronary circulation.Generally, these legions may be classified as follows:

Type Characteristic A Prebranch stenosis not involving the ostium of theside branch; B Postbranch stenosis of the parent vessel not involvingthe origin of the side branch; C Stenosis encompassing the side branchbut not involving the ostium; D Stenosis involving the parent vessel andostium of the side branch; E Stenosis involving the ostium of the sidebranch only; and F Stenosis discretely involving the parent vessel andostium of the side branch.

See Atlas of Interventional Cardiology (Popma et al.), 1994, pages77-79, the contents of which are hereby incorporated by reference. Thepresence of bifurcation lesions is predictive of increased proceduralcomplications including acute vessel closure.

Detailed classification of other bifurcated body passageways isrelatively undeveloped given the lack of non-surgical treatmentapproaches.

U.S. Pat. No. 4,994,071 (MacGregor) discloses a bifurcating stentapparatus. The particular design incorporates a series of generallyparallel oriented loops interconnected by a sequence of “half-birch”connections. The lattice structure of the illustrated stent isconstructed of wire. The use of such wire is important to obtain theloop structure of the illustrated design. The use of a wire loopconstruction is disadvantageous since it is complicated to manufactureand the resulting stent is subject to expansion variability (e.g.variable post-expansion distortion and the like).

U.S. Pat. Nos. 3,993,078 (Bergentz et al.) and 5,342,387 (Summers) alsodisclose and illustrate a bifurcated stent design constructed of wire.These designs suffer from the same disadvantages as the design describedin the previous paragraph.

It would be desirable to have a reliable, expandable bifurcated stentsince this would be useful in treating aneurysms, blockages and otherailments. It would be further desirable to have a practical method forproducing such a stent. It would also be desirable if such a stent wasrelatively easy to install.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a novel expandablebifurcated stent which obviates or mitigates at least one of theabove-mentioned disadvantages of the prior art.

It is another object of the present invention to provide a novel methodfor the manufacture of an expandable bifurcated stent.

It is another object of the present invention to provide a novel methodfor implanting an expandable bifurcated stent.

Accordingly, in one of its aspects, the present invention provides anexpandable bifurcated stent comprising a proximal end and a distal endin communication with one another, the proximal end comprising a primarypassageway and the distal end comprising a pair of secondarypassageways, each secondary passageway in communication with the primarypassageway at a first intersection, the stent being expandable from afirst, contracted position to a second, expanded position upon theapplication of a radially outward force exerted on the stent, each ofthe primary passageway and the secondary passageways being constructedof a tubular wall having a porous surface, at least one connectionportion being disposed at the first intersection for reinforcing thefirst intersection.

In another of its aspects, the present invention provides expandablebifurcated stent comprising a proximal end and a distal end incommunication with one another, the proximal end comprising a primarypassageway and the distal end comprising a pair of secondarypassageways, each secondary passageway in communication with the primarypassageway at a first intersection, the stent being expandable from afirst, contracted position to a second, expanded position upon theapplication of a radially outward force exerted on the stent, each ofthe primary passageway and the secondary passageways having a poroussurface, at least one connection portion interconnecting the pair ofsecondary passageways for reinforcing the first intersection.

In yet another of its aspects, the present invention provides a methodfor production of a bifurcated stent comprising the step of connecting afirst stent section to a second stent section, the first stent sectionhaving an end thereof adapted for connection to an opening disposedalong the length of a second stent section.

In yet another of its aspects, the present invention provides a methodfor production of a bifurcated stent comprising the steps of:

(i) connecting a first stent section to a second stent section toprovide a connection portion;

(ii) provide an opening in the connection portion;

(iii) connecting a third stent section to the connection portion.

In yet another of its aspects, the present invention provides a methodfor production of a bifurcated stent comprising the steps of:

passing a first stent section having a first opening disposed along alength thereof through a second stent section having a second openingdisposed along a length thereof, the first stent section having adiameter less than a diameter of the second stent section;

passing a leading end of the first stent section through the secondopening of the second stent section; and

substantially aligning the first opening and the second opening withrespect to one another.

In yet another of its aspects, the present invention provides a methodfor delivery to a target body passageway of an expandable bifurcatedstent comprising a proximal end and a distal end in communication withone another, the proximal end comprising a primary passageway and thedistal end comprising a pair of secondary passageways, the stent beingexpandable from a first, contracted position to a second, expandedposition upon the application of a radially outward force exerted on thestent, each of the primary passageway and the secondary passageway beingconstructed of a tubular wall having a porous surface, the methodcomprising the steps of:

disposing the stent in the first, contracted position on a catheter;

inserting the stent and catheter within the target body passageway bycatheterization of the target body passageway;

exerting a radially outward expansive force on the stent such that thestent assumes the second, expanded position and is urged against thetarget body passageway.

Thus, an aspect of the present invention relates to the provision of anexpandable bifurcated stent constructed of a tubular wall having aporous surface. As used throughout this specification, the term “tubularwall”, when used in relation to a stent, is intended to mean asubstantially cylindrical tube which subsequently has been subjected toan etching (e.g. by laser, chemical or other suitable means) or similartechnique to remove pre-selected portions of the cylindrical tubethereby providing a porous surface on the tube—this is distinct from astent constructed of wire bent to a selected shape/design. To theknowledge of the Applicant's, an expandable bifurcated stent having sucha tubular wall has heretofore been unknown.

As used throughout this specification, the term “bifurcated stent” isintended to have a broad meaning and encompasses any stent having aprimary passageway to which is connected at least two secondarypassageways. Thus, trifurcated stents are encompassed herein. Further,one of the secondary passageways can be a continuation of the primarypassageway with the result that the other secondary passageway isessentially a side branch to the primary passageway.

The Applicant's have also discovered that various repeating patterns inthe porous surface of the tubular wall are particularly advantageous.Generally, the repeating pattern is a polygon having a pair of sidewalls substantially parallel to the longitudinal axis of the stentpassageway in question, a first concave-shaped wall and a secondconvex-shaped wall connecting the side walls. The various repeatingpatterns which are useful in the context of the present invention aredisclosed in the following copending patent applications filed in thename of the assignee of the present invention:

Canadian patent application number 2,134,997 (filed Nov. 3, 1994);

Canadian patent application number 2,171,047 (filed Mar. 5, 1996);

Canadian patent application number 2,175,722 (filed May 3, 1996);

Canadian patent application number 2,185,740 (filed Sep. 17, 1996);

International patent application PCT/CA97/00151 (filed Mar. 5, 1997);and

International patent application PCT/CA97/00152 (filed Mar. 5, 1997);

the contents of each of which are hereby incorporated by reference(hereinafter collectively referred to as the “Divysio patentapplications”).

The present bifurcated stent may be constructed from any suitablestarting material. Preferably, the starting material is a thin tube of ametal or alloy (non-limiting examples include stainless steel, titanium,tantalum, nitinol, Elgiloy, NP35N and mixtures thereof) which would thenhave sections thereof cut or etched out to leave a repeating pattern,inter alia, such as one or more of those disclosed in the Divysio patentapplications.

The stent of the present invention may further comprise a coatingmaterial thereon. The coating material may be disposed continuously ordiscontinuously on the surface of the stent. Further, the coating may bedisposed on the interior and/or the exterior surface(s) of the stent.The coating material may be one or more of a biologically inert material(e.g. to reduce the thrombogenicity of the stent), a medicinalcomposition which leaches into the wall of the body passageway afterimplantation (e.g. to provide anticoagulant action, to deliver apharmaceutical to the body passageway and the like) and the like.

The stent is preferably provided with a biocompatible coating, in orderto minimize adverse interaction with the walls of the body vessel and/orwith the liquid, usually blood, flowing through the vessel. The coatingis preferably a polymeric material, which is generally provided byapplying to the stent a solution or dispersion of preformed polymer in asolvent and removing the solvent. Non-polymeric coating material mayalternatively be used. Suitable coating materials, for instancepolymers, may be polytetraflouroethylene or silicone rubbers, orpolyurethanes which are known to be biocompatible. Preferably, however,the polymer has zwitterionic pendant groups, generally ammoniumphosphate ester groups, for instance phosphoryl choline groups oranalogues thereof. Examples of suitable polymers are described inpublished International patent applications WO-A-93/16479 andWO-A-93/15775. Polymers described in those specifications arehemo-compatible as well as generally biocompatible and, in addition, arelubricious. When a biocompatible coating is used, It is important toensure that the surfaces of the stent are completely coated in order tominimize unfavourable interactions, for instance with blood, which mightlead to thrombosis.

This good coating can be achieved by suitable selection of coatingconditions, such as coating solution viscosity, coating technique and/orsolvent removal step.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be described with reference tothe accompanying drawings wherein like numerals designate like parts andin which:

FIG. 1 illustrates a side elevation of a bifurcated stent in accordancewith the present invention;

FIGS. 2-4 illustrate a first embodiment of a method for production of abifurcated stent;

FIG. 5 illustrates a second embodiment of a method for production of abifurcated stent;

FIGS. 6a and 6 b illustrate a post-treatment of a bifurcated stent whichhas been produced according to the methods illustrated in FIGS. 2-5;

FIGS. 7 and 8 illustrate a third embodiment of a method for productionof a bifurcated stent;

FIG. 9 illustrates a post-treated bifurcated stent which has beenproduced according to the method illustrated in FIGS. 7 and 8;

FIGS. 10 and 11 illustrate a fourth embodiment of a method forproduction of a bifurcated stent;

FIG. 12 illustrates a cross-section of a bifurcated body passageway intowhich the a bifurcated stent produced according to the present method ofmanufacture is being delivered;

FIG. 13 illustrates a cross-section of a bifurcated body passageway inwhich the bifurcated stent is positioned in a first, contractedposition;

FIG. 14 illustrates a cross-section of a bifurcated body passageway inwhich the bifurcated stent is positioned in a second, expanded position;

FIGS. 15 and 16 illustrate a side elevation of another bifurcated stentin accordance with the present invention;

FIGS. 17-22 illustrate various preferred features of the bifurcatedstent illustrated in FIGS. 15 and 16.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to FIG. 1, there is illustrated a stent 10. Stent 10comprises a proximal end 15 and a distal end 20. Proximal end 15comprises a primary passageway 25. Distal end 20 comprises a pair ofsecondary passageways 30,35. Secondary passageways 30,35 are connectedto primary passageway 25 at an intersection point 40.

As will be apparent to those of skill in the art, stent 10 incorporatesthe porous surface design illustrated in copending Canadian patentapplication number 2,134,944, referred to above. As discussed above,this design may be varied to incorporate other designs such as thosedisclosed in the other Divysio patent applications.

With reference to FIGS. 2-4, an embodiment of the present method forproduction of a bifurcated stent is illustrated. For ease ofillustration, the porous surface of the tubular wall of the stent is notillustrated.

As illustrated, a first stent section 45 comprises a cylindrical tubehaving a bevelled cut 50 made adjacent one end of the cylindrical tube.Those of skill in the art will recognize that bevelled cut 50 may beincorporated into first stent section 45 during or after the productionof first stent section 45. Specifically, it is possible to produce firststent section 45 having a pre-selected porous design which includesbevelled cut 50 via a computer programmable, high precision laseretching technique. Alternatively, it is possible to use another etchingtechnique to produce first stent section 45 without bevelled cut 50 andthereafter use a precision jig or other means to cut first stent section45 to produce bevelled cut 50.

Similarly, a second stent section 55 is provided and includes radialcuts 56,57 and a longitudinal cut 58. Radial cuts 56,57 and longitudinalcuts 58 may be produced in second stent section 55 in the mannerdiscussed in the previous paragraph with respect to the production ofbevelled cut 50 in first stent section 45. Thereafter, a flap portion 51of first stent section 45 is folded away from bevelled cut 50.Similarly, a pair of flap 52,53 are folded away from longitudinal cut 58to expose an opening 54.

First stent section 45 is then lowered to cover opening 54 of secondstent section 55. Flaps 52,53 are folded to overlap a portion of firststent section 45. Flap 51 is folded to overlap a portion of second stentsection 55. With reference to FIG. 4, it is particularly preferred toadapt the geometry of flaps 52,53 of second stent section 55 such thatvarious of the struts disposed in flaps 52,53 overlap with or arejuxtaposed (in plan view) along at least a portion of the length thereofwith the struts on first stent section 45 (this is illustrated in moredetail hereinbelow with reference to FIG. 16). Preferably, the degree ofsuch overlap or juxtaposition is sufficient to:

(i) facilitate affixing the flaps 52,53 of second stent section 55 tofirst stent section 45;

(ii) achieve uniform expansion of the stent junction without occurrenceof substantial distortion; and

(iii) avoid the occurrence of “stent trap” or “stent jail” (usually theresult of cracking, buckling or other distortion at the junction of adeployed bifurcated stent making difficult or impossible to deliver afurther stent through the stent).

At this point, the flaps may be secured to the respective stent sectionsby any suitable means such as spot welding (e.g. by a laser or othersuitable means), loops, clips and the like. The preferred method ofaffixing the flaps to the respective stent section is to spot weld them.

A particular advantage of the process illustrated in FIGS. 2-4 is thatintersection point 40 (FIG. 1—overlapping flaps not illustrated forclarity) of the resulting stent is reinforced by virtue of dispositionof the flaps overlapping a portion of the respective stent sections.

As will be apparent to those of skill in the art, in certaincircumstances, it may be possible and even desirable to reduce the sizeof or even eliminate flap 51. Further, in certain circumstances, it maybe possible or ever desirable to trim one or both of flaps 52,53 priorto connection of first stent section 45 to second stent section 55.

With reference to FIG. 5, there is illustrated another embodiment of thepresent method for manufacture of a bifurcated stent. In thisembodiment, flap 51 (FIGS. 2 and 3) is simply cut away from first stentsection 45 a. Further, an oval opening 54 a is cut into second stentsection 55 a (i.e. there are no flaps affixed to second stent section 55a). Stent section 45 a is then lowered on and connected to second stentsection 55 a. First stent section 45 a and second stent section 55 a maybe connected to another in the manner described hereinabove withreference to FIG. 2-4.

With reference to FIG. 6a, there is illustrated the stent produced bythe methods illustrated in FIGS. 2-4. During production of the stent, itis desirable to minimize the angle between first stent section 45 andsecond stent section 55. Even with this effort, it is preferred that theadjacent termini of first stent section 45 and section stent section 55are subjected to application of gentle squeezing or other sufficientforce in the direction of arrows A to facilitate catheterization of thestent. The result of such post-production treatment of the stent isillustrated in FIG. 6b.

With reference to FIGS. 7 and 8, there is illustrated yet anotherembodiment of the present method for manufacture of a bifurcated stent.In this embodiment, a pair of first stent sections 45 b are secured oraffixed to one another. Thereafter, an apex portion 46 b of theresulting construction is removed exposing an opening 54 b. A secondstent section 55 b is then connected to opening 54 b provided by thecombination of first stent sections 45 b. The manner of securing secondstent section 55 b to the periphery of opening 54 b created by firststent sections 45 b is not particularly restricted and may be effectedas discussed hereinabove. As will be appreciated by those of skill inthe art, it is possible and, in certain circumstances, desirable, tohave one or more flaps on one or move of first stent sections 45 b andsecond stent section 55 b. Such flaps would be used in the mannerdiscussed hereinabove in respect of FIGS. 2-4 to overlap a portion ofthe opposite stent section.

With reference to FIG. 9, there is illustrated the stent producedaccording to the method illustrated in FIGS. 7 and 8 afterpost-treatment in the manner discussed above in respect of FIGS. 6a and6 b. That is, first stent sections 45 b are subjected to application ofgentle squeezing or other sufficient force in the direction of arrows Bto facilitate catheterization of the stent.

With reference to FIGS. 10 and 11, there is illustrated yet anotherembodiment of the present method for manufacture of a bifurcated stent.In this embodiment, a first stent section 45 c is provided with anopening 54 c. A second stent section 55 c is provided with an opening 56c. Second stent section 55 c has a diameter slightly less than that offirst stent section 45 c. The difference in diameter between first stentsection 45 c and second stent section 55 c is sufficient to enablecoaxial movement of the stent sections with respect to one another withcausing damage to either stent section.

As illustrated by arrow C in FIG. 10, the end of second stent section 55c is coaxially fed into an end of first stent section 45 c. Once theleading end of second stent section 55 c reaches opening 54 c of firststent section 45 c, it is pulled through opening 54 c as illustrated byarrow D in FIG. 10. Second stent section 55 c is pulled through opening54 c until opening 56 c is aligned with opening 54 c—this is illustratedby dashed oval E in FIG. 11.

When practising the method illustrated in FIGS. 10 and 11, care shouldbe taken to design openings 54 c and 56 c so that they are in alignmentwhen the trailing end of second stent section 55 c is flush with thetrailing end of first stent section 45 c. Further, region F (FIG. 11) ofthe resulting bifurcated stent is “double reinforced” since it containsa coaxial disposition of first stent section 45 c and second stentsection 55 c. Accordingly, it is possible and, in some cases evendesirable, to modify the design of the respective stent sections in thisregion so that the overall expansion and relative flexibility/rigidityof the stent in this region is commensurate with that of the remainingportion of the stent (i.e. the secondary passageways which branch offfrom region F in FIG. 11).

While the embodiment illustrated in FIGS. 10 and 11 illustrates theresultant bifurcated stent having a coaxial, overlapping arrangement ofstent sections flush at one end, it will be appreciated by those ofskill in the art that the length of first stent section 45 c or secondstent section 55 c may be shortened thereby minimizing the size ofregion F in FIG. 11.

With reference to FIGS. 12-14 , there is illustrated a bifurcated bodypassageway 150 comprised of a proximal passageway 155 and a pair ofdistal passageways 160,165. As illustrated, bifurcated body passageway150 comprises a Type “D” Bifurcation lesion having characteristicblockages 170,175,180.

Stent 10 is delivered to bifurcated body passageway 150 in the followingmanner. Initially, a pair of guidewires 185,190 are inserted intoproximal passageway 155 such that guidewire 185 enters distal passageway160 and guidewire 190 enters distal passageway 165. The manner by whichthe guidewires are inserted is conventional and within the purview of aperson skilled in the art.

As illustrated, stent 10 is positioned in association with a pair ofcatheters 195,200 (for clarity, the interior of stent 10 is not shown).Catheter 195 has associated with it a balloon 205. Catheter 200 hasassociated with it a balloon 210. Balloons 205,210 substantially fillprimary passageway 25 of stent 10. Balloon 205 substantially fillssecondary passageway 30 of stent 10. Balloon 210 substantially fillssecondary passageway 35 of stent 10.

The stent/catheter/balloon combination is delivered through proximalpassageway 155 with the aid of guidewires 185,190. As thestent/catheter/balloon combination approaches distal passageways160,165, predisposition of guidewires 185,190 serves to separatesecondary passageways 30,35 to be disposed in distal passageways160,165, respectively. Thus, as illustrated in FIG. 13, stent 10 ispositioned in place.

Once stent 10 is in position, balloons 205,210 are expanded resulting inimplantation of stent 10 in the corresponding interior surfaces ofproximal passageway 155 and distal passageways 160,165. Uponimplantation of stent 10, balloons 205,210 are collapsed. Thereafter,catheters 195,200 and guidewires 185,190 have been removed leaving theimplanted stent 10 shown in FIG. 14. As illustrated in FIG. 14,blockages 170,175,180 are bulged radially outwardly in combination withthe appropriate portions of proximal passageway 155 and distalpassageways 160,165 resulting in a reduction in the overall blockage inbifurcated body passage 150.

It will be apparent to those of skill in the art that implantation ofstent 10 can be accomplished by various other means. For example, it iscontemplated that it is possible to substitute the pair ofcatheter/balloon combinations illustrated in FIGS. 12 and 13 with asingle, bifurcated catheter/balloon design which mimics the design ofthe stent. Thus, in this modification, the balloon and guidewire wouldbe design to mimic the bifurcated design of the stent. As furtheralternative, it is contemplated that the stent can be made of a suitablematerial which will expand when bifurcated body passageway 150 isflushed with a liquid having an elevated temperature (e.g. 150° F.-160°F.). Further, stent 10 can be designed to expand upon the application ofmechanical forces other than those applied by a balloon/catheter. Stillfurther, stent 10 can be designed self-expanding (e.g. by constructingstent from material such as nitinol and the like) to be implanted asdescribed above. In this embodiment, the radially outward force exertedon the stent would be generated within the stent itself.

With reference to FIGS. 15-22, there is illustrated another preferredbifurcated stent in accordance with the present invention. As will beapparent to those of skill in the art, the stent illustrated in FIGS.15-22 shares many of the features of stent 10 illustrated in FIG. 1.

Thus, with reference to FIGS. 15 and 16, there is illustrated a stent100. FIG. 15 is a side elevation of stent 100 without the porous surfaceillustrated (for clarity). FIG. 16 is a side elevation of an enlargedportion of stent 100 with the porous surface illustrated. Stent 100comprises a proximal end 102 and a distal end 104. Proximal end 102comprises a primary passageway 103. Distal end 104 comprises a pair ofsecondary passageways 105,106. Secondary passageways 105,106 areconnected to primary passageway 103 at an intersection point 107—thenature of intersection point 107 will be further discussed hereinbelow.It is intersection point 107 which distinguishes stent 100 in FIG. 16from stent 10 in FIG. 1.

As will be apparent to those of skill in the art, stent 100 incorporatesthe porous surface design illustrated in copending Canadian patentapplication number 2,134,944, referred to above. As discussed above,this design may be varied to incorporate other designs such as thosedisclosed in the other Divysio patent applications.

With reference to FIGS. 17-19, manufacture of stent 100 will bediscussed. Generally, the manufacture of stent 100 is similar to themanufacture of stent 10 illustrated in FIGS. 14 and discussedhereinabove. The principle difference in the manufacture of stent 100 isthe use of a modified first stent section 108.

First stent section 108 is constructed from a substantially cylindricaltube 109. A porous surface 110 is disposed on a major portion ofcylindrical tube 109. A first connection tab 111 and a second connectiontab 112 are also disposed on cylindrical tube 109. As discussedhereinabove, it is possible to produce first section 108 comprisingporous 110, first connection tab 111 and second connection tab 112 usingcomputer programmable, high precision laser etching techniques or byother etching techniques in combination with precision jig techniques.This results in an end of porous surface 110 comprising first connectiontab 111, second connection tab 112 and a bevelled edge 113. The productof the cutting techniques is illustrated in FIG. 18.

FIG. 19 is an enlarged perspective view of a portion of first connectiontab 111 (second connection tab 112 is preferably the same). Asillustrated, first connection tab 111 comprises a stem 114 and a head115. Preferably, stem 114 and/or head 115 are curved to have a shapecomplementary to the outer surface of the second section to which firststent section 108 is connected (discussed in more detailed hereinbelow).Stem 114 and head 115 comprise a plurality of slots 116 disposedtherein. Slots 116 may be disposed in stem 114 and head 115 by the useof a computer programmable, high precision laser as described above.Preferably, slots 116 are disposed throughout the thickness of stem 114and head 115. Slots 116 may be may have a straight or taperedcross-section. Preferably, slots 116 have a thickness in the range offrom about 0.0015 to about 0.004 inches. Head 115 further comprisessolid (i.e., slot-free or non-porous) regions 117,118.

Thus, in the embodiment illustrated in FIG. 19, slots 116 serve to froma porous surface in first connection tab 111 (second connection tab 112is preferably the same). While it is preferred to have such a poroussurface disposed in the connection tabs, the precise nature of theporosity is not particularly restricted. The provision of a poroussurface, particularly at head 115, facilitates expansion of theconnection tab while minimizing or avoiding the occurrence of crackingor distortion.

After the production of first stent section 108, first connection tab111 and second connection tab 112 are bent or otherwise moved to besubstantially collinear with the periphery of bevelled edge 113 (i.e.,as illustrated in FIG. 118). At this point, first stent section 108 maybe connected to another stent section of a design similar to secondstent section 55 discussed hereinabove with reference to FIGS. 2-4—seeintersection point 107 in FIG. 16. In this embodiment, as in theembodiments illustrated in FIGS. 2-4, it is preferred to adapt thegeometry of flaps 52,53 of second stent section 55 such that various ofthe struts disposed in flaps 52,53 overlap along at a portion of thelength thereof with the struts on first stent section 108. See, forexample, regions G and H in FIG. 16 which illustrates an embodiment ofsuch partial overlap and juxtaposition (in plan view). First connectiontab 111 and second connection tab 112 may be secured to the second stentsection as described above. Specifically, it is particularly preferredto connect solid (i.e., non-porous) regions 117,118 to the stent sectionportion.

The benefits accruing from the use of first stent section 108 in theproduction a bifurcated stent include:

1. The provision of at least one solid (i.e., non-porous) region in theconnection tabs facilitates attachment of the respective stent sectionsto one another (e.g., laser welding is facilitated significantly);

2. The provision of a porous surface in at least a portion of theconnection tabs facilitates bending thereof for connection of therespective stent sections; and

3. The provision of slots 116, particularly in second connection tab 112(see FIG. 15), allows the slots to function as a solid state valve atthe “crotch” of the bifurcated stent thereby providing sealed,reinforcement of the bifurcated stent in this crucial region—this isillustrated in FIG. 20 which depicts tapered openings for slots 116 inthe apex of the bend in stem 114.

FIG. 21 illustrates an alternate embodiment of the embodimentillustrated in FIGS. 15-20. Specifically, in FIG. 21, second stentsection 55, otherwise the same as that described hereinabove withreference to FIGS. 14, is adapted to include a landing 119 for receivinga solid (i.e. non-slot or non-porous) connection tab 120. Landing 119may be connected to connection tab 120 as described hereinabove.

With reference to FIG. 22, there is illustrated a variant to theembodiment illustrated in FIG. 21. Specifically, in FIG. 22, aconnection tab 121 having the entire surface thereof slotted andotherwise porous is connected to landing 119.

While this invention has been described with reference to illustrativeembodiments, this description is not intended to be construed in alimiting sense. Various modifications of the illustrative embodiments,as well as other embodiments of the invention, will be apparent topersons skilled in the art upon reference to this description. Forexample, while first connection tab 111 and second connection tab 112have been illustrated as being attached to first stent portion 108, itis possible to have these tabs integral with second stent portion 55.Alternatively, the connection tabs do not have to integral with eitherof the stent portions and, instead, can be custom-designed, independentconnection tabs which are affixed to both stent portions. Still further,it is possible for the connection tabs (integral or independent) to havea different thickness than either of the stent sections. It is thereforecontemplated that the appended claims will cover any such modificationsor embodiments.

What is claim is:
 1. An expandable bifurcated stent comprising: aproximal end and a distal end in communication with one another, theproximal end comprising a primary passageway and the distal endcomprising a pair of secondary passageways, each secondary passageway incommunication with the primary passageway at a first intersection, thestent being expandable from a first, contracted position to a second,expanded position upon the application of a radially outward forceexerted on the stent, each of the primary passageway and the secondarypassageways being constructed of a tubular wall in the form of asubstantially cylindrical tube having preselected portions thereofremoved to define a porous surface, at least one of the secondarypassageways having a bevel cut in an end thereof.
 2. The bifurcatedstent defined in claim 1, wherein the stent comprises a first stentsection connected to a second stent section.
 3. The bifurcated stentdefined in claim 2, wherein an end of the first stent section isconnected to an opening disposed along a length of the second stentsection.
 4. The bifurcated stent defined in claim 3, wherein a firstconnection portion is disposed at an end of the first stent section andis connected to the second stent section.
 5. The bifurcated stentdefined in claim 4, wherein the first connection portion as integralwith an end of the first stent section.
 6. The bifurcated stent definedin claim 4, wherein the first connection portion comprises a poroussection and a non-porous section, the non-porous section connected tothe second stent section.
 7. The bifurcated stent defined in claim 6,wherein the porous section comprises a plurality of elongate slots. 8.The bifurcated stent defined in claim 7, wherein the elongate slotstraverse the thickness of the at least one connection portion.
 9. Thebifurcated stent defined in claim 7, wherein the elongate slots aredisposed substantially orthogonal to a longitudinal axis of the firststent section.
 10. The bifurcated stent defined in claim 9, wherein thesecond stent section comprises a second connection portion along atleast a portion of the periphery of the opening, the second connectionportion connected to the first stent section.
 11. The bifurcated stentdefined in claim 2, wherein the first stent section and the second stentsection are coaxially disposed with respect to one another along atleast a portion of the primary passageway.
 12. The bifurcated stentdefined in claim 2, wherein the first stent section and the second stentsection are coaxially disposed with respect to one another alongsubstantially the entire length of the primary passageway.
 13. Thebifurcated stent defined in claim 2, wherein the first stent section andthe second stent section are connected to one another and to a thirdstent section, at least one of the stent sections comprising the primarypassageway and each of the other to stent sections comprising asecondary passageway.
 14. The bifurcated stent defined in claim 1,wherein the at least one connection portion interconnects the pair ofsecondary passageways.
 15. The bifurcated stent defined in claim 1,wherein the at least one connection portion connects one of the pair ofsecond passageways to the primary passageway.
 16. A method forproduction of a bifurcated stent comprising the step of: connecting afirst stent section to a second stent section, the first stent sectionhaving a bevel cut in an end thereof adapted for connection to anopening disposed along the length of a second stent section; the firststent section and the second stent section being constructed of atubular wall in the form of a substantially cylindrical tube havingpreselected portions thereof removed to define a porous surface.
 17. Themethod defined in claim 16, wherein the end of the first stent sectionadapted for connection is bevelled with respect to a longitudinal axisof the first stent section.
 18. The method defined in claim 16,comprising the further step of disposing at least one first flap portionat the end of the first stent section adapted for connection to aportion the second stent section.
 19. The method defined in claim 18,wherein the at least one flap portion comprises a connection tab havinga non-porous surface disposed on at least a portion thereof.
 20. Themethod defined in claim 18, wherein the at least one flap portioncomprises a connection tab having a porous surface disposed on at leasta portion thereof.
 21. The method defined in claim 20, wherein theporous surface comprises a plurality of substantially elongate slots.22. The method defined in claim 18, wherein the at least one flapportion comprises a connection tab having both a porous surface andnon-porous surface disposed thereon.
 23. The method defined in claim 22,wherein the porous surface comprises a plurality of substantiallyelongate slots.
 24. The method defined in claim 18, wherein the at leastone first flap portion is produced by folding from the end of the firststent section adjacent the bevelled cut.
 25. The method defined in claim18, wherein prior to the connecting step, the at least one first flapportion is trimmed to a reduced size.
 26. The method defined in claim18, comprising the further step of overlapping at least one first flapportion of the first stent section on to a portion of the second stentsection.
 27. The method defined in claim 26, wherein the connecting stepcomprises welding the at least one first flap portion of the first stentsection to the second stent section.
 28. The method defined in claim 18,wherein, prior to the connecting step, the at least one first flapportion is removed.
 29. The method defined in claim 16, comprising thefurther step of disposing at least one second flap portion at aperiphery of the opening dispose d along the length of the second stentsection.
 30. The method defined in claim 16, comprising the further stepof disposing a pair of second flap portions at a periphery of theopening disposed along the length of the second stent section.
 31. Themethod defined in claim 30, wherein, prior to the connecting step, atleast one second flap portion is trimmed to a reduced size.
 32. Themethod defined in claim 30, comprising the further step of overlappingthe at least one second flap portion of the second stent section on to aportion of the first stent section.
 33. The method defined in claim 32,wherein the connecting step comprises welding the at least one secondflap portion of the second stent section to the first stent section. 34.The method defined in claim 30, wherein, prior to the connecting step,at least one second flap portion is removed.
 35. The method defined inclaim 16, comprising the further steps of producing the second stentsection by: providing a pair of third stent section each third stentsections having an end thereof bevelled with respect to a longitudinalaxis of the third stent section; joining the pair of third stentsections in a complementary manner at each bevelled end thereof toprovide a substantially V-shaped stent section; and removing an apexportion of the V-shaped stent section to define the second stent sectionhaving an opening therein.
 36. The method defined in claim 35, whereinthe connecting step comprises connecting the end of the stent section tothe opening defined in the V-shaped stent section.
 37. The methoddefined in claim 16, wherein the connecting step comprises welding firststent section to the second stent section.
 38. A method for productionof a bifurcated stent comprising steps of: passing a first stent sectionhaving a first opening disposed along a length thereof through a secondstent section having a second opening disposed along a length thereof,the first stent section having a diameter less than a diameter of thesecond stent section, the first opening comprising a bevel cut in an endof the first stent section; passing a leading end of first stent sectionthrough the second opening of the second stent section; andsubstantially aligning the first opening and the second opening withrespect to one another; the first stent section and the second stentsection being constructed of a tubular wall in the form of substantiallycylindrical tube having preselected portions thereof removed to define aporous surface.
 39. An expandable bifurcated stent comprising: aproximal end and a distal end in communication with one another, theproximal end comprising a primary passageway and the distal endcomprising a pair of secondary passageways, each secondary passageway incommunication with the primary passageway at a first intersection, asecondary passageway having a bevel cut in an end thereof adjacent thefirst intersection, the stent being expandable from a first, connectedposition to a second, expanded position upon the application of aradially outward force exerted on the stent, each of the primarypassageway and the secondary passageways having a porous surface, atleast one connection portion interconnecting the pair of secondarypassageways for reinforcing the first intersection.
 40. An expandablemonotubular stent, comprising: a substantially cylindrical tube having adistal end and a proximal end, wherein said substantially cylindricaltube has a porous surface over a major portion of said tube, and whereina beveled cut is provided adjacent to the distal end of said monotubularstent, the bevelled cut defining a plane extending through the distalend of the monotubular stent at an angle with respect to a longitudinalaxis of the monotubular stent to form a portion of an ellipse, themonotubular stent being expandable from a first, contracted position toa second, expanded position upon the application of a force exertedradially outward on the monotubular stent.
 41. The monotubular stent ofclaim 40, wherein said bevelled cut extends through less than all of anouter surface of the monotubular stent.
 42. The monotubular stent ofclaim 40, wherein said stent has a porous surface section and anon-porous surface section.
 43. The monotubular stent of claim 40,wherein said porous surface comprises a plurality of elongated slots.44. The monotubular stent of claim 43, wherein said elongated slots aredisposed substantially orthogonal to a longitudinal axis of saidmonotubular stent.
 45. An expandable stent, comprising: a substantiallycylindrical tube having a distal end and a proximal end, wherein saidsubstantially cylindrical tube has a porous surface over a major portionof said tube, and wherein a beveled cut is provided adjacent to thedistal end of said monotubular stent, the monotubular stent beingexpandable from a first, contracted position to a second, expandedposition upon the application of a force exerted radially outward on themonotubular stent, wherein said monotubular stent having a beveled cuttherein is incorporated into a bifurcated stent.
 46. A method ofproducing an expandable monotubular stent, comprising the steps of:providing a substantially cylindrical tube having a distal end and aproximal end; providing a porous surface design over a major portion ofsaid tube; and providing a bevelled cut adjacent to the distal end ofsaid monotubular stent, the bevelled cut defining a plane extendingthrough the distal end of the monotubular stent at an angle with respectto a longitudinal axis of the monotubular stent to form a portion of anellipse, the monotubular stent being expandable from a first, contractedposition to a second, expanded position upon the application of a forceexerted radially outward on the monotubular stent.
 47. The method ofclaim 46, wherein the monotubular stent is produced using etching. 48.The method of claim 47, wherein the etching is performed using acomputer-programmable laser.
 49. The method of claim 46, wherein thebeveled cut is incorporated into said monotubular stent as the stent isbeing produced.
 50. The method of claim 46, wherein the beveled cut isincorporated into said monotubular stent after it is produced.
 51. Themethod of claim 50, wherein the beveled cut is made using a precisionjig.
 52. The method of claim 46, wherein the beveled cut is beveled withrespect to a longitudinal axis of said monotubular stent.
 53. A methodof producing an expandable stent, comprising the steps of: providing asubstantially cylindrical tube having a distal end and a proximal end;providing a porous surface design over a major portion of said tube;providing a bevelled cut adjacent to the distal end of said monotubularstent, the monotubular stent being expandable from a first, contractedposition to a second, expanded position upon the application of a forceexerted radially outward on the monotubular stent; and using saidmonotubular stent to produce a bifurcated stent.